First Person Shooters that descend into a grind.
What I mean by this is the whole field locks down and the small space in between teams turns into a WW1 style killzone that no one can pass through. The number 1 reason for this is splash damage disproportionate to the size of the level. This is the main reason I've had a better experience with the battlefield series on Xbox 360 than on PC; the popular custom servers tend to turn up the player counts which turns everything into a hell of infinite grenade spam down short passages. Great for leveling up, but... not great as an actual game.
Just got Nuclear Dawn for 2.50 because pocket change, and was immediately reminded of Battlefield 2142. Not JUST because the graphics and loadouts were very similar, but also because you couldn't go anywhere without fucking dying. For some brilliant reason the class with the shotgun and the highest health class have a grenade launcher and rocket launcher respectively, AND every class except the rocket guys can get 3 grenades which are devastating compared to everything else in the game. Now, this was on a tight map and you don't get the rocket/grenade launcher until later on in the game, so it MIGHT not always descend into that. But still... how long has 2142 been out that you couldn't learn from its mistakes?
On that topic, a second pet peeve that is in both 2142 and Nuclear Dawn: the shimmer cloak. That's were the cloak is visible because it distorts everything behind it. Seriously, this NEVER works. Experienced players can always see right through it. If your character's power is being invisible, they should ACTUALLY be invisible. It worked in TF2, it works in every MOBA ever, there's no excuse anymore.